This invention relates to the detection of the presence of organic fluids or oils, and more particularly to a method and apparatus for sensing the presence of organic liquids or oils whether in an aqueous solution or on the surface of an aqueous stream or solid body, the sensing being particularly useful for the determination of the presence of organic contaminants in or on liquid or solid substrates.
It is known, as disclosed in Haigh U.S. Pat. No. 3,520,806, that organic liquids can be separated from aqueous substrates by contacting the substrate and organic liquids with a particulate cross-linked organic liquid-insoluble, organic liquid swellable polymer with the organic liquids imbibed therein. Utilizing the imbibing polymer principle a number of useful products have evolved. For example, in Hall, et al U.S. Pat. Nos. 3,750,688 and 3,958,590 and in Haigh, et al U.S. Pat. No. 4,024,882 valves are proposed having a bed of swellable polymer particles or beads which imbibe organic liquid materials to swell and close flow communication therethrough of an aqueous stream contaminated with organic liquid material. In Haigh, et al U.S. Pat. No. 3,686,827 and in Hall, et al U.S. Pat. No. 4,172,031 the imbibing bead principle is utilized for separating organic vapors from air and organic liquids through an aqueous stream respectively. In Larson, et al U.S. Pat. No. 4,302,337 an organic liquid imbibing coating is applied to the surface of a foraminous body and swells to plug the interstitial spaces within the body when contacted by an organic fluid thereby to close the flow of an aqueous contaminated stream therethrough to permit removal of the organic liquid from the stream.
As aforesaid these disclosures are concerned with the removal of organic fluids from a contaminated stream or to the shutting of the flow of such a stream in a conduit system. They are thus directed to closed systems in which a bed of imbiber beads may be placed for separation of the contaminants. There are, however, circumstances where the detection of such contaminants is desirable but where the fluid does not flow in a defined conduit system. For example, in situations where a contaminated fluid is spilled on the surface of water or on a solid surface such as on dry ground, pavement or floors. The aforesaid patents are not directed to such conditions.
Several sensing devices are known which can detect the presence of organic fluids such as solvents, hydrocarbons, halogenated solvents, aromatics, organic fuels, lubricating oils and the like. Some such devices employ the use of detectors which sense changes in thermal conductivity, density or viscosity. These physical characteristics are used to detect the presence of organic fluids as opposed to the presence of water or aqueous solutions. The known detectors are sophisticated electronic devices for providing warning signals to personnel that a spill may have occurred from a tank or other storage basin. The disadvantage of most of these devices is that they are very expensive, and may depend on apparatus which can be rendered inoperative by a hostile environment and, since the equipment is sensitive, inaccurate readings are possible.
Consequently, it is a primary object of the present invention to provide a method and apparatus for accurately detecting the presence of organic fluids on various substrates.
It is another object of the present invention to provide a method and apparatus for detecting the presence of organic fluids in or on the surface of an aqueous stream or a solid surface.
It is a further object of the present invention to provide a method and apparatus for detecting the presence of organic fluids in or on the surface of an aqueous or solid substrate and for providing a signal warning of such detection.
It is a still further object of the present invention to provide a sensing strip formed from a pair of strips coated with an imbibing latex polymer and joined together at an overlapping joint which softens upon contact with an organic fluid and upon being placed in tension disjoins to signal the presence of the organic fluid.
Accordingly, an organic fluid detecting strip is formed from separate strips of an imbibing latex emulsion sorbing material which have cooperating ends coated with an imbibing latex polymer and joined together at their common coated ends. The other ends of the strips may have a tensile force applied thereto so that the strips disjoin at the joint upon softening of the imbibing polymer when contacted with an organic fluid. The ends of the strips to be joined are coated with the imbibing latex by immersing those ends in an imbibing latex emulsion such as disclosed in the aforesaid Larson et al U.S. Pat. No 4,302,337, the disclosure of which is incorporated herein by reference. Thereafter the strips are joined and allowed to dry and fuse together, or the strips may be dryed without joining and thereafter the imbiber latex is softened by an organic fluid and the strips are then joined and dried.
In the specific form of the invention the strips are constructed from a fabric-like material and loops may be formed at the ends remote from the joined imbibing latex ends. Tension applying means may be connected to the looped ends so that the strips separate when an organic fluid contacts the joined ends.
The term "organic fluid" as employed herein is defined in a manner similar to the term "oil" defined in the aforesaid U.S. Pat. No. 4,302,337. Thus, by "organic fluid" is meant organic liquids or oils which are generally immiscible with water or soluble to not more than two weight percent in water at 25.degree. C. and atmospheric pressure. Such organic fluids include: petroleum oils such as kerosene, lubricating oil, gasoline, jet fuel, and fuel oil. Other organic fluids include: benzene, toluene, xylene, ethylbenzene, aliphatic hydrocarbons such as hexane, octane, dodecane, eicosane, position isomers thereof, cyclic hydrocarbons such as cyclohexane, ethylcyclohexane, ketones such as 2-octenone, 4-dodecenone, and chlorinated solvents such as 1,1,1-trichloroethane, o-dichlorobenzene and the like. This list is not all inclusive but is merely representative of those organic fluids detectable by the imbibing latex polymer. Moreover, the term "fluid" as used herein is used in its ordinary sense and includes liquids, gases and vapors.
The imbibing latex coated on the strip comprises a generally coherent mass of organic liquid imbibing particles swellable in an organic fluid from about 2 to 50 times their unswollen volume. The coating comprises an imbibing latex polymer which has the property of being substantially insoluble in, but capable of being swollen by, that is, imbibing, one or more nonaqueous organic liquids.